1. Field of the Invention
The present invention is related to interconnection systems. In particular, the present invention is related to virtual midplanes.
2. Description of Related Art
As data communication rates become higher and higher to meet demanding applications, interconnecting printed circuit boards (PCB) or cards in communication systems becomes more and more important. Signal transmission rate depends on a number of factors. One important factor is the length of the signal trace on the PCB. The shorter the length, the faster the signal can propagate. In addition, resistance and capacitance of the signal trace have impact on interconnecting system design. When the signal density is high, the interconnection of the signals for high speed applications becomes a challenge.
FIG. 1 shows a prior art interconnection system. For illustrative purposes, only two front cards are shown. The prior art system 100 includes two front cards 110 and 120, a midplane 130, and a rear card 140.
The front cards 110 and 120 have signal traces 118 and 128 and front connectors 115 and 125, respectively. The signal traces are terminated with contact points in the corresponding connectors. One objective of the interconnection system is to connect the signal traces 118 on the front card 110 to the corresponding signal traces 128 on the front card 120. The connectors 115 and 125 are typically full-length connectors having as many contact points as necessary to accommodate the interconnecting of the signal traces on the front cards.
The midplane has mating connectors 132 and 134 to mate with the front card connectors 115 and 125. The midplane 130 also has signal traces 138 running between the mating connectors 132 and 134 to form electrical connections for the contact points in the connectors 115 and 125. The rear card 140 provides additional area for signal traces. The rear card 140 is interfaced to the midplane via a rear connector.
The prior art system 100 has a number of disadvantages. First, the full-length configuration of the connectors 115 and 125 reduces the routing flexibility on the front cards 110 and 120 and the midplane 130. Second, the interconnecting signal trace lengths are long, resulting in higher propagation delay and lower speed. Third, there are two terminations at the two ports, resulting higher cost and additional delay due to additional capacitance and resistance. Fourth, the complexity and hardware cost for the midplane can be very high. The midplane may have many internal layers to accommodate all the interconnecting signals.
Therefore, there is a need to have an efficient technique for interconnecting cards in a high speed environment.
The present invention is a method and apparatus for interconnection system. A first connector located on a first card provides first contacts for first signal traces on the first card. The first connector has a first housing enclosing the first contacts and a first extension portion. A second connector located on a second card provides second contacts for second signal traces on the second card. The second connector has a second housing enclosing the second contacts. The second connector is coupled to the first connector when the first and second housings are mated such that the first and second cards are substantially perpendicular to each other, the second card is aligned on the first extension portion. There is no need for an intermediate card and an additional connector.
According to one embodiment of the present invention, the first connector further has a first inter-card spacing portion to provide spacing between the first card and a third card positioned in a substantially parallel direction with the first card, and the second connector further has a second extension portion to provide alignment for the first card when the first and second connectors are coupled and a second inter-card spacing portion to provide spacing between the second card and a fourth card positioned in a substantially parallel direction with the second card.
The advantages of the invention include high signal transmission rates, increased interconnection reliability, high signal density, routing flexibility, balanced mechanical structure, and reduced overall mechanical stress.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.